public boolean isValid(final String value, final ConstraintValidatorContext context) {
        return determineValid(value);
    }

    /**
     * Determines if the given value is a valid cron expression.
     * @param value the value to validate
     * @return true if valid, false otherwise
     */
    protected boolean determineValid(final String value) {
        if (StringUtil.isNotBlank(value) && !LaCronUtil.isCronExpValid(value)) {

    @Test
    public void test_determineValid_nullAndBlank() {
        assertTrue(validator.determineValid(null));
        assertTrue(validator.determineValid(""));
        assertTrue(validator.determineValid(" "));
        assertTrue(validator.determineValid("   "));
        assertTrue(validator.determineValid("\t"));
        assertTrue(validator.determineValid("\n"));
    }

    @Test
    public void test_initialize() {